As is known, rehabilitation is an important practice to assist an infirm patient to recover full or partial neuromuscular or muscular control of a part of the body, limb or organ, such as the arms or legs and related joints, such as hips, knees, elbow, etc. It has long been shown that, even in patients who have lost the ability to autonomously perform movements, the execution of assisted movements of the part of the body to be rehabilitated allows to recover first a neural control and then a muscular control on that part of the body. For example, rehabilitation of the lower limbs is required for recovery of patients with post-stroke injuries or parkinsonian syndromes, in order to regain or improve posture control and postural equilibrium.
Rehabilitation requires in general execution of a number of repetitive physical exercises involving the affected limb, and assistance to the patient is needed during execution of these exercises, particularly at the early stages of rehabilitation (when the patient has little control of the affected part of the body). Assistance to the patient is often provided manually by one or more therapists, but it is not always possible to perform all the required exercises with the correct procedure.
Accordingly, rehabilitation systems and apparatuses have been designed, in the form of more or less complex harnesses, for example adapted to be placed hanging from the ceiling, that allow to support the weight of the patient and thus help the same patient in the execution of the rehabilitation exercises. However, these apparatuses are complex and expensive and offer a limited amount of flexibility and modularity in adapting to the specific needs of the various patients, and, even more importantly, do not involve neurologically, as well as physically the patient.
Recently, designing of exoskeleton devices has been proposed as a promising solution for assisting patients during rehabilitation treatments. Exoskeleton devices, including supporting frames of motorized segments to be applied to the patient, have indeed the potentiality to offer a versatile solution to be used by the patient in the execution of the different repetitive rehabilitation exercises. However, designing of such exoskeleton devices poses a serious challenge in terms of their control logic, and reliable exoskeleton devices for rehabilitation have not yet been designed and are still not currently available.
Indeed, research in the field of exoskeleton devices has been focused mainly on strength augmentation in order to boost the performances of the wearer, for example for military or heavy work applications. These devices do not address the problem of providing patient support and postural stability, since they imply the presence of an able-bodied wearer.
In spite of many results in the field of postural equilibrium of biped robotics, fewer studies in the field of rehabilitation have tackled the joint aspects of postural stability (instead of strength) augmentation and patient compliance, and the few exoskeletons proposed have shown evident limitations and failed to address all the requirements and needs for patient recovery, among which: an accurate position control, in order to maintain the exoskeleton (and wearer) dynamically stable or constrain it to follow a planned reference trajectory; a controlled patient “compliance” (i.e. the capability to control the resistance perceived by the patient to voluntary movements), in order to involve the patient in the rehabilitation exercises and tutoring the improvements in the patient abilities; and, either whenever dynamical exercises are performed or quiet standing is maintained, a controlled postural equilibrium, in order to interact with the patient for maintaining or timely regaining equilibrium and correcting any erroneous patient posture. In particular, the control systems that have been proposed for the known exoskeletons have not proven sufficiently robust and reliable to accommodate all the above requirements.